Gravity Probe B

Testing Einstein's Universe

WEEKLY HIGHLIGHTS FOR WEEK ENDING 2 MARCH 2001:

COMPLETED CM:16 PAYLOAD ACOUSTIC TEST COMPLETE
The GP-B payload successfully completed a protqual acoustic test at 145.1 dB SPL, thus completing an important program milestone. The steps
performed in this program area during the past week include the installation of the payload on to the Payload Acoustic Test Stand Pedestals
in the B/159 Acoustic Cell. Sound level instrumentation, final accelerometer checkouts were then performed followed by a -6 dB test run.
After a data review of the -6 dB run, the full 0 dB run was carried out. The payload was then taken off the pedestals and the process was initiated
to return the payload to Stanford to allow completion of Payload Test II.

UNCAGED GYROSCOPE PASSES TWO LAUNCH-LOAD RELATED SHAKE TESTS
An uncaged flight-like gyroscope successfully operated after being subjected to a 1.65 grms shake. This environment simulates the qual level
acoustic launch load. The gyroscope performance tests included leviation, cavity exploration, and spindown rate measurements. This was the first
test in a series of tests designed to determine if science gyroscopes can be launched uncaged. In the second test of this series an uncaged
gyroscope was subjected to a 2.5 g sine sweep for a 50 second duration thus simulating the expected loads at liftoff. The gyroscope met all
specifications before and after the test.

SUCCESSFULLY OPERATED ECU UV LAMPS OVER FULL TEMPERATURE RANGE
Both UV lamps in the flight ECU were operated in vacuum at 20 C and at 50 C. This demonstration, with the ECU's cover off, confirms the suspected
root cause of the UV lamp test anomaly. The plan is to put vent holes in the ECU box to allow adequate venting of the box and thereby allow
operation of the UV over the required operating range. A minor test anomaly associated with one of the eight UV switches is under investigation.